Peaking the Luma video part of S-video - Videokarma.org TV - Video

wa2ise · #1 02-15-2009, 06:06 PM

Popped the lid off my Channel Master CM7000 converter box, the one with S-video. I wanted to add a little peaking to the luma, by paralleling a small 470pF surface mount cap across the source 75 ohm surface mount resistor that resides between the output driver and the S-video jack.

My choice of 470pF was partially driven by what I could scrounge off some junk boards, and the desire to have a few dB more higher frequency response, at about 5MHz. And without seriously impacting the group delay response, which is important with video.

Used the below code, cut and paste it using notepad, and save it as XLC.htm

<html><head>
<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">

<title>L or C Reactance Calculator</title>


</head><body bgcolor="#ffffdf">

<center>
<h1>L or C Reactance Calculator</h1>
</center>
<blockqoute><blockquote>
Enter any two known values and press "Calculate" to solve for the others.
For example, a 1000pF capacitor or a 25.3 uH inductor will have 159 Ohms
of reactance at a frequency of 1 MegaHertz. Fields should be reset to 0
before doing a new calculation.
<p></p><h4><b></b><center>
<b>Inductive Reactance (Xl) = 2 * Pi * F * L
<br>
Capacitive Reactance (Xc) = 1 / ( 2 * Pi * F * C )
<br>
Resonant Frequency (Fo) = 1 / ( 2 * Pi * SquareRoot(LC) )
</b></center></h4>
</blockquote>

<script language="Javascript">
var PI=3.14159
var C
var L
var F
var X
function Process(form)
{
L=L*1
F=F
C=C/1000000
if (C > 0 && F > 0) { X = (1/(2*PI*F*C)); L=X/(2*PI*F)}
if (L > 0 && F > 0) { X = (2*PI*F*L); C=1/(2*PI*X*F) }
if (C > 0 && X > 0) { F = 1/(2*PI*X*C); L= X/(2*PI*F) }
if (L > 0 && X > 0) { F = X/(2*PI*L); C=1/(2*PI*X*F) }
if (F > 0 && X > 0) { L = X/(2*PI*F); C=1/(2*PI*X*F) }
if (C > 0 && L > 0) {
X=Math.sqrt((L*C),2)
F=(1/(2*PI*X))
X=2*PI*F*L
}
L=Math.round(L*1000)
L=L/1000
F=Math.round(F*100000000)
F=F/100000000
C=Math.round(C*10000000)
C=C/10
X=Math.round(X*1000)
X=X/1000

form.C.value = C
form.L.value = L
form.F.value = F
form.X.value = X
}

function SetC(C1) { C = C1.value }
function SetL(L1) { L = L1.value }
function SetX(X1) { X = X1.value }
function SetF(F1) { F = F1.value }

function ClearForm(form){
C=0
L=0
X=0
F=0
form.C.value = 0
form.L.value = 0
form.X.value = 0
form.F.value = 0
}
</script>

<center>
<form method="post">
<table border="5">
<tbody><tr>
<td><div align="center"><b>Capacitance<br>(picofarads)</b></div></td>
<td><div align="center"><b>Inductance<br>(microhenrys)</b></div></td>
<td><div align="center"><b>Reactance<br>(Ohms)</b></div></td>
<td><div align="center"><b>Frequency<br>(MegaHertz)</b></div></td>
<td><input onclick="Process(this.form)" value="Calculate" type="button"></td>
</tr>
<tr>
<td><div align="center"><input name="C" size="12" onchange="SetC(this)" type="text"></div></td>
<td><div align="center"><input name="L" size="12" onchange="SetL(this)" type="text"></div></td>
<td><div align="center"><input name="X" size="12" onchange="SetX(this)" type="text"></div></td>
<td><div align="center"><input name="F" size="12" onchange="SetF(this)" type="text"></div></td>
<td><div align="center"><input value=" Reset " onclick="ClearForm(this.form)" type="button"></div>
</td></tr>
</tbody></table>
</form>
<a href="http://ourworld.compuserve.com/homepages/Bill_Bowden/XLC.htm">Adapted from http://ourworld.compuserve.com/homepages/Bill_Bowden/XLC.htm</a>
<br>
<a href="http://ourworld.compuserve.com/homepages/Bill_Bowden/homepage.htm#menu">menu</a>
</center>
<br>
</blockqoute></body></html>